/*
** $Id: ldo.c,v 2.157 2016/12/13 15:52:21 roberto Exp $
** Stack and Call structure of Lua
** See Copyright Notice in lua.h
*/

#define ldo_c
#define LUA_CORE

#include "lprefix.h"


#include <setjmp.h>
#include <stdlib.h>
#include <string.h>

#include "lua.h"

#include "lapi.h"
#include "ldebug.h"
#include "ldo.h"
#include "lfunc.h"
#include "lgc.h"
#include "lmem.h"
#include "lobject.h"
#include "lopcodes.h"
#include "lparser.h"
#include "lstate.h"
#include "lstring.h"
#include "ltable.h"
#include "ltm.h"
#include "lundump.h"
#include "lvm.h"
#include "lzio.h"



#define errorstatus(s)  ((s) > LUA_YIELD)


/*
** {======================================================
** Error-recovery functions
** =======================================================
*/

/*
** LUAI_THROW/LUAI_TRY define how Lua does exception handling. By
** default, Lua handles errors with exceptions when compiling as
** C++ code, with _longjmp/_setjmp when asked to use them, and with
** longjmp/setjmp otherwise.
*/
#if !defined(LUAI_THROW)                /* { */

#if defined(__cplusplus) && !defined(LUA_USE_LONGJMP)   /* { */

/* C++ exceptions */
#define LUAI_THROW(L,c)     throw(c)
#define LUAI_TRY(L,c,a) \
    try { a } catch(...) { if ((c)->status == 0) (c)->status = -1; }
#define luai_jmpbuf     int  /* dummy variable */

#elif defined(LUA_USE_POSIX)                /* }{ */

/* in POSIX, try _longjmp/_setjmp (more efficient) */
#define LUAI_THROW(L,c)     _longjmp((c)->b, 1)
#define LUAI_TRY(L,c,a)     if (_setjmp((c)->b) == 0) { a }
#define luai_jmpbuf     jmp_buf

#else                           /* }{ */

/* ISO C handling with long jumps */
#define LUAI_THROW(L,c)     longjmp((c)->b, 1)
#define LUAI_TRY(L,c,a)     if (setjmp((c)->b) == 0) { a }
#define luai_jmpbuf     jmp_buf

#endif                          /* } */

#endif                          /* } */



/* chain list of long jump buffers */
struct lua_longjmp {
    struct lua_longjmp* previous;
    luai_jmpbuf b;
    volatile int status;  /* error code */
};


static void seterrorobj( lua_State* L, int errcode, StkId oldtop ) {
    switch ( errcode ) {
    case LUA_ERRMEM: {  /* memory error? */
        setsvalue2s( L, oldtop, G( L )->memerrmsg ); /* reuse preregistered msg. */
        break;
    }

    case LUA_ERRERR: {
        setsvalue2s( L, oldtop, luaS_newliteral( L, "error in error handling" ) );
        break;
    }

    default: {
        setobjs2s( L, oldtop, L->top - 1 ); /* error message on current top */
        break;
    }
    }

    L->top = oldtop + 1;
}


l_noret luaD_throw( lua_State* L, int errcode ) {
    if ( L->errorJmp ) { /* thread has an error handler? */
        L->errorJmp->status = errcode;  /* set status */
        LUAI_THROW( L, L->errorJmp ); /* jump to it */
    }
    else {   /* thread has no error handler */
        global_State* g = G( L );
        L->status = cast_byte( errcode ); /* mark it as dead */

        if ( g->mainthread->errorJmp ) { /* main thread has a handler? */
            setobjs2s( L, g->mainthread->top++, L->top - 1 ); /* copy error obj. */
            luaD_throw( g->mainthread, errcode ); /* re-throw in main thread */
        }
        else {   /* no handler at all; abort */
            if ( g->panic ) { /* panic function? */
                seterrorobj( L, errcode, L->top ); /* assume EXTRA_STACK */

                if ( L->ci->top < L->top ) {
                    L->ci->top = L->top;    /* pushing msg. can break this invariant */
                }

                lua_unlock( L );
                g->panic( L ); /* call panic function (last chance to jump out) */
            }

            abort();
        }
    }
}


int luaD_rawrunprotected( lua_State* L, Pfunc f, void* ud ) {
    unsigned short oldnCcalls = L->nCcalls;
    struct lua_longjmp lj;
    lj.status = LUA_OK;
    lj.previous = L->errorJmp;  /* chain new error handler */
    L->errorJmp = &lj;
    LUAI_TRY( L, &lj,
              ( *f )( L, ud );
            );
    L->errorJmp = lj.previous;  /* restore old error handler */
    L->nCcalls = oldnCcalls;
    return lj.status;
}

/* }====================================================== */


/*
** {==================================================================
** Stack reallocation
** ===================================================================
*/
static void correctstack( lua_State* L, TValue* oldstack ) {
    CallInfo* ci;
    UpVal* up;
    L->top = ( L->top - oldstack ) + L->stack;

    for ( up = L->openupval; up != NULL; up = up->u.open.next ) {
        up->v = ( up->v - oldstack ) + L->stack;
    }

    for ( ci = L->ci; ci != NULL; ci = ci->previous ) {
        ci->top = ( ci->top - oldstack ) + L->stack;
        ci->func = ( ci->func - oldstack ) + L->stack;

        if ( isLua( ci ) ) {
            ci->u.l.base = ( ci->u.l.base - oldstack ) + L->stack;
        }
    }
}


/* some space for error handling */
#define ERRORSTACKSIZE  (LUAI_MAXSTACK + 200)


void luaD_reallocstack( lua_State* L, int newsize ) {
    TValue* oldstack = L->stack;
    int lim = L->stacksize;
    lua_assert( newsize <= LUAI_MAXSTACK || newsize == ERRORSTACKSIZE );
    lua_assert( L->stack_last - L->stack == L->stacksize - EXTRA_STACK );
    luaM_reallocvector( L, L->stack, L->stacksize, newsize, TValue );

    for ( ; lim < newsize; lim++ ) {
        setnilvalue( L->stack + lim );    /* erase new segment */
    }

    L->stacksize = newsize;
    L->stack_last = L->stack + newsize - EXTRA_STACK;
    correctstack( L, oldstack );
}


void luaD_growstack( lua_State* L, int n ) {
    int size = L->stacksize;

    if ( size > LUAI_MAXSTACK ) { /* error after extra size? */
        luaD_throw( L, LUA_ERRERR );
    }
    else {
        int needed = cast_int( L->top - L->stack ) + n + EXTRA_STACK;
        int newsize = 2 * size;

        if ( newsize > LUAI_MAXSTACK ) {
            newsize = LUAI_MAXSTACK;
        }

        if ( newsize < needed ) {
            newsize = needed;
        }

        if ( newsize > LUAI_MAXSTACK ) { /* stack overflow? */
            luaD_reallocstack( L, ERRORSTACKSIZE );
            luaG_runerror( L, "stack overflow" );
        }
        else {
            luaD_reallocstack( L, newsize );
        }
    }
}


static int stackinuse( lua_State* L ) {
    CallInfo* ci;
    StkId lim = L->top;

    for ( ci = L->ci; ci != NULL; ci = ci->previous ) {
        if ( lim < ci->top ) {
            lim = ci->top;
        }
    }

    lua_assert( lim <= L->stack_last );
    return cast_int( lim - L->stack ) + 1; /* part of stack in use */
}


void luaD_shrinkstack( lua_State* L ) {
    int inuse = stackinuse( L );
    int goodsize = inuse + ( inuse / 8 ) + 2 * EXTRA_STACK;

    if ( goodsize > LUAI_MAXSTACK ) {
        goodsize = LUAI_MAXSTACK;    /* respect stack limit */
    }

    if ( L->stacksize > LUAI_MAXSTACK ) { /* had been handling stack overflow? */
        luaE_freeCI( L );    /* free all CIs (list grew because of an error) */
    }
    else {
        luaE_shrinkCI( L );    /* shrink list */
    }

    /* if thread is currently not handling a stack overflow and its
       good size is smaller than current size, shrink its stack */
    if ( inuse <= ( LUAI_MAXSTACK - EXTRA_STACK ) &&
            goodsize < L->stacksize ) {
        luaD_reallocstack( L, goodsize );
    }
    else  /* don't change stack */
        condmovestack( L, {}, {} ); /* (change only for debugging) */
}


void luaD_inctop( lua_State* L ) {
    luaD_checkstack( L, 1 );
    L->top++;
}

/* }================================================================== */


/*
** Call a hook for the given event. Make sure there is a hook to be
** called. (Both 'L->hook' and 'L->hookmask', which triggers this
** function, can be changed asynchronously by signals.)
*/
void luaD_hook( lua_State* L, int event, int line ) {
    lua_Hook hook = L->hook;

    if ( hook && L->allowhook ) { /* make sure there is a hook */
        CallInfo* ci = L->ci;
        ptrdiff_t top = savestack( L, L->top );
        ptrdiff_t ci_top = savestack( L, ci->top );
        lua_Debug ar;
        ar.event = event;
        ar.currentline = line;
        ar.i_ci = ci;
        luaD_checkstack( L, LUA_MINSTACK ); /* ensure minimum stack size */
        ci->top = L->top + LUA_MINSTACK;
        lua_assert( ci->top <= L->stack_last );
        L->allowhook = 0;  /* cannot call hooks inside a hook */
        ci->callstatus |= CIST_HOOKED;
        lua_unlock( L );
        ( *hook )( L, &ar );
        lua_lock( L );
        lua_assert( !L->allowhook );
        L->allowhook = 1;
        ci->top = restorestack( L, ci_top );
        L->top = restorestack( L, top );
        ci->callstatus &= ~CIST_HOOKED;
    }
}


static void callhook( lua_State* L, CallInfo* ci ) {
    int hook = LUA_HOOKCALL;
    ci->u.l.savedpc++;  /* hooks assume 'pc' is already incremented */

    if ( isLua( ci->previous ) &&
            GET_OPCODE( *( ci->previous->u.l.savedpc - 1 ) ) == OP_TAILCALL ) {
        ci->callstatus |= CIST_TAIL;
        hook = LUA_HOOKTAILCALL;
    }

    luaD_hook( L, hook, -1 );
    ci->u.l.savedpc--;  /* correct 'pc' */
}


static StkId adjust_varargs( lua_State* L, Proto* p, int actual ) {
    int i;
    int nfixargs = p->numparams;
    StkId base, fixed;
    /* move fixed parameters to final position */
    fixed = L->top - actual;  /* first fixed argument */
    base = L->top;  /* final position of first argument */

    for ( i = 0; i < nfixargs && i < actual; i++ ) {
        setobjs2s( L, L->top++, fixed + i );
        setnilvalue( fixed + i ); /* erase original copy (for GC) */
    }

    for ( ; i < nfixargs; i++ ) {
        setnilvalue( L->top++ );    /* complete missing arguments */
    }

    return base;
}


/*
** Check whether __call metafield of 'func' is a function. If so, put
** it in stack below original 'func' so that 'luaD_precall' can call
** it. Raise an error if __call metafield is not a function.
*/
static void tryfuncTM( lua_State* L, StkId func ) {
    const TValue* tm = luaT_gettmbyobj( L, func, TM_CALL );
    StkId p;

    if ( !ttisfunction( tm ) ) {
        luaG_typeerror( L, func, "call" );
    }

    /* Open a hole inside the stack at 'func' */
    for ( p = L->top; p > func; p-- ) {
        setobjs2s( L, p, p - 1 );
    }

    L->top++;  /* slot ensured by caller */
    setobj2s( L, func, tm ); /* tag method is the new function to be called */
}


/*
** Given 'nres' results at 'firstResult', move 'wanted' of them to 'res'.
** Handle most typical cases (zero results for commands, one result for
** expressions, multiple results for tail calls/single parameters)
** separated.
*/
static int moveresults( lua_State* L, const TValue* firstResult, StkId res,
                        int nres, int wanted ) {
    switch ( wanted ) { /* handle typical cases separately */
    case 0:
        break;  /* nothing to move */

    case 1: {  /* one result needed */
        if ( nres == 0 ) { /* no results? */
            firstResult = luaO_nilobject;    /* adjust with nil */
        }

        setobjs2s( L, res, firstResult ); /* move it to proper place */
        break;
    }

    case LUA_MULTRET: {
        int i;

        for ( i = 0; i < nres; i++ ) { /* move all results to correct place */
            setobjs2s( L, res + i, firstResult + i );
        }

        L->top = res + nres;
        return 0;  /* wanted == LUA_MULTRET */
    }

    default: {
        int i;

        if ( wanted <= nres ) { /* enough results? */
            for ( i = 0; i < wanted; i++ ) { /* move wanted results to correct place */
                setobjs2s( L, res + i, firstResult + i );
            }
        }
        else {   /* not enough results; use all of them plus nils */
            for ( i = 0; i < nres; i++ ) { /* move all results to correct place */
                setobjs2s( L, res + i, firstResult + i );
            }

            for ( ; i < wanted; i++ ) { /* complete wanted number of results */
                setnilvalue( res + i );
            }
        }

        break;
    }
    }

    L->top = res + wanted;  /* top points after the last result */
    return 1;
}


/*
** Finishes a function call: calls hook if necessary, removes CallInfo,
** moves current number of results to proper place; returns 0 iff call
** wanted multiple (variable number of) results.
*/
int luaD_poscall( lua_State* L, CallInfo* ci, StkId firstResult, int nres ) {
    StkId res;
    int wanted = ci->nresults;

    if ( L->hookmask & ( LUA_MASKRET | LUA_MASKLINE ) ) {
        if ( L->hookmask & LUA_MASKRET ) {
            ptrdiff_t fr = savestack( L, firstResult ); /* hook may change stack */
            luaD_hook( L, LUA_HOOKRET, -1 );
            firstResult = restorestack( L, fr );
        }

        L->oldpc = ci->previous->u.l.savedpc;  /* 'oldpc' for caller function */
    }

    res = ci->func;  /* res == final position of 1st result */
    L->ci = ci->previous;  /* back to caller */
    /* move results to proper place */
    return moveresults( L, firstResult, res, nres, wanted );
}



#define next_ci(L) (L->ci = (L->ci->next ? L->ci->next : luaE_extendCI(L)))


/* macro to check stack size, preserving 'p' */
#define checkstackp(L,n,p)  \
  luaD_checkstackaux(L, n, \
    ptrdiff_t t__ = savestack(L, p);  /* save 'p' */ \
    luaC_checkGC(L),  /* stack grow uses memory */ \
    p = restorestack(L, t__))  /* 'pos' part: restore 'p' */


/*
** Prepares a function call: checks the stack, creates a new CallInfo
** entry, fills in the relevant information, calls hook if needed.
** If function is a C function, does the call, too. (Otherwise, leave
** the execution ('luaV_execute') to the caller, to allow stackless
** calls.) Returns true iff function has been executed (C function).
*/
int luaD_precall( lua_State* L, StkId func, int nresults ) {
    lua_CFunction f;
    CallInfo* ci;

    switch ( ttype( func ) ) {
    case LUA_TCCL:  /* C closure */
        f = clCvalue( func )->f;
        goto Cfunc;

    case LUA_TLCF:  /* light C function */
        f = fvalue( func );
Cfunc: {
            int n;  /* number of returns */
            checkstackp( L, LUA_MINSTACK, func ); /* ensure minimum stack size */
            ci = next_ci( L ); /* now 'enter' new function */
            ci->nresults = nresults;
            ci->func = func;
            ci->top = L->top + LUA_MINSTACK;
            lua_assert( ci->top <= L->stack_last );
            ci->callstatus = 0;

            if ( L->hookmask & LUA_MASKCALL ) {
                luaD_hook( L, LUA_HOOKCALL, -1 );
            }

            lua_unlock( L );
            n = ( *f )( L ); /* do the actual call */
            lua_lock( L );
            api_checknelems( L, n );
            luaD_poscall( L, ci, L->top - n, n );
            return 1;
        }

    case LUA_TLCL: {  /* Lua function: prepare its call */
        StkId base;
        Proto* p = clLvalue( func )->p;
        int n = cast_int( L->top - func ) - 1; /* number of real arguments */
        int fsize = p->maxstacksize;  /* frame size */
        checkstackp( L, fsize, func );

        if ( p->is_vararg ) {
            base = adjust_varargs( L, p, n );
        }
        else {  /* non vararg function */
            for ( ; n < p->numparams; n++ ) {
                setnilvalue( L->top++ );    /* complete missing arguments */
            }

            base = func + 1;
        }

        ci = next_ci( L ); /* now 'enter' new function */
        ci->nresults = nresults;
        ci->func = func;
        ci->u.l.base = base;
        L->top = ci->top = base + fsize;
        lua_assert( ci->top <= L->stack_last );
        ci->u.l.savedpc = p->code;  /* starting point */
        ci->callstatus = CIST_LUA;

        if ( L->hookmask & LUA_MASKCALL ) {
            callhook( L, ci );
        }

        return 0;
    }

    default: {  /* not a function */
        checkstackp( L, 1, func ); /* ensure space for metamethod */
        tryfuncTM( L, func ); /* try to get '__call' metamethod */
        return luaD_precall( L, func, nresults ); /* now it must be a function */
    }
    }
}


/*
** Check appropriate error for stack overflow ("regular" overflow or
** overflow while handling stack overflow). If 'nCalls' is larger than
** LUAI_MAXCCALLS (which means it is handling a "regular" overflow) but
** smaller than 9/8 of LUAI_MAXCCALLS, does not report an error (to
** allow overflow handling to work)
*/
static void stackerror( lua_State* L ) {
    if ( L->nCcalls == LUAI_MAXCCALLS ) {
        luaG_runerror( L, "C stack overflow" );
    }
    else if ( L->nCcalls >= ( LUAI_MAXCCALLS + ( LUAI_MAXCCALLS >> 3 ) ) ) {
        luaD_throw( L, LUA_ERRERR );    /* error while handing stack error */
    }
}


/*
** Call a function (C or Lua). The function to be called is at *func.
** The arguments are on the stack, right after the function.
** When returns, all the results are on the stack, starting at the original
** function position.
*/
void luaD_call( lua_State* L, StkId func, int nResults ) {
    if ( ++L->nCcalls >= LUAI_MAXCCALLS ) {
        stackerror( L );
    }

    if ( !luaD_precall( L, func, nResults ) ) { /* is a Lua function? */
        luaV_execute( L );    /* call it */
    }

    L->nCcalls--;
}


/*
** Similar to 'luaD_call', but does not allow yields during the call
*/
void luaD_callnoyield( lua_State* L, StkId func, int nResults ) {
    L->nny++;
    luaD_call( L, func, nResults );
    L->nny--;
}


/*
** Completes the execution of an interrupted C function, calling its
** continuation function.
*/
static void finishCcall( lua_State* L, int status ) {
    CallInfo* ci = L->ci;
    int n;
    /* must have a continuation and must be able to call it */
    lua_assert( ci->u.c.k != NULL && L->nny == 0 );
    /* error status can only happen in a protected call */
    lua_assert( ( ci->callstatus & CIST_YPCALL ) || status == LUA_YIELD );

    if ( ci->callstatus & CIST_YPCALL ) { /* was inside a pcall? */
        ci->callstatus &= ~CIST_YPCALL;  /* continuation is also inside it */
        L->errfunc = ci->u.c.old_errfunc;  /* with the same error function */
    }

    /* finish 'lua_callk'/'lua_pcall'; CIST_YPCALL and 'errfunc' already
       handled */
    adjustresults( L, ci->nresults );
    lua_unlock( L );
    n = ( *ci->u.c.k )( L, status, ci->u.c.ctx ); /* call continuation function */
    lua_lock( L );
    api_checknelems( L, n );
    luaD_poscall( L, ci, L->top - n, n ); /* finish 'luaD_precall' */
}


/*
** Executes "full continuation" (everything in the stack) of a
** previously interrupted coroutine until the stack is empty (or another
** interruption long-jumps out of the loop). If the coroutine is
** recovering from an error, 'ud' points to the error status, which must
** be passed to the first continuation function (otherwise the default
** status is LUA_YIELD).
*/
static void unroll( lua_State* L, void* ud ) {
    if ( ud != NULL ) { /* error status? */
        finishCcall( L, *( int* )ud );    /* finish 'lua_pcallk' callee */
    }

    while ( L->ci != &L->base_ci ) { /* something in the stack */
        if ( !isLua( L->ci ) ) { /* C function? */
            finishCcall( L, LUA_YIELD );    /* complete its execution */
        }
        else {  /* Lua function */
            luaV_finishOp( L ); /* finish interrupted instruction */
            luaV_execute( L ); /* execute down to higher C 'boundary' */
        }
    }
}


/*
** Try to find a suspended protected call (a "recover point") for the
** given thread.
*/
static CallInfo* findpcall( lua_State* L ) {
    CallInfo* ci;

    for ( ci = L->ci; ci != NULL; ci = ci->previous ) { /* search for a pcall */
        if ( ci->callstatus & CIST_YPCALL ) {
            return ci;
        }
    }

    return NULL;  /* no pending pcall */
}


/*
** Recovers from an error in a coroutine. Finds a recover point (if
** there is one) and completes the execution of the interrupted
** 'luaD_pcall'. If there is no recover point, returns zero.
*/
static int recover( lua_State* L, int status ) {
    StkId oldtop;
    CallInfo* ci = findpcall( L );

    if ( ci == NULL ) {
        return 0;    /* no recovery point */
    }

    /* "finish" luaD_pcall */
    oldtop = restorestack( L, ci->extra );
    luaF_close( L, oldtop );
    seterrorobj( L, status, oldtop );
    L->ci = ci;
    L->allowhook = getoah( ci->callstatus ); /* restore original 'allowhook' */
    L->nny = 0;  /* should be zero to be yieldable */
    luaD_shrinkstack( L );
    L->errfunc = ci->u.c.old_errfunc;
    return 1;  /* continue running the coroutine */
}


/*
** Signal an error in the call to 'lua_resume', not in the execution
** of the coroutine itself. (Such errors should not be handled by any
** coroutine error handler and should not kill the coroutine.)
*/
static int resume_error( lua_State* L, const char* msg, int narg ) {
    L->top -= narg;  /* remove args from the stack */
    setsvalue2s( L, L->top, luaS_new( L, msg ) ); /* push error message */
    api_incr_top( L );
    lua_unlock( L );
    return LUA_ERRRUN;
}


/*
** Do the work for 'lua_resume' in protected mode. Most of the work
** depends on the status of the coroutine: initial state, suspended
** inside a hook, or regularly suspended (optionally with a continuation
** function), plus erroneous cases: non-suspended coroutine or dead
** coroutine.
*/
static void resume( lua_State* L, void* ud ) {
    int n = *( cast( int*, ud ) ); /* number of arguments */
    StkId firstArg = L->top - n;  /* first argument */
    CallInfo* ci = L->ci;

    if ( L->status == LUA_OK ) { /* starting a coroutine? */
        if ( !luaD_precall( L, firstArg - 1, LUA_MULTRET ) ) { /* Lua function? */
            luaV_execute( L );    /* call it */
        }
    }
    else {   /* resuming from previous yield */
        lua_assert( L->status == LUA_YIELD );
        L->status = LUA_OK;  /* mark that it is running (again) */
        ci->func = restorestack( L, ci->extra );

        if ( isLua( ci ) ) { /* yielded inside a hook? */
            luaV_execute( L );    /* just continue running Lua code */
        }
        else {  /* 'common' yield */
            if ( ci->u.c.k != NULL ) { /* does it have a continuation function? */
                lua_unlock( L );
                n = ( *ci->u.c.k )( L, LUA_YIELD, ci->u.c.ctx ); /* call continuation */
                lua_lock( L );
                api_checknelems( L, n );
                firstArg = L->top - n;  /* yield results come from continuation */
            }

            luaD_poscall( L, ci, firstArg, n ); /* finish 'luaD_precall' */
        }

        unroll( L, NULL ); /* run continuation */
    }
}


LUA_API int lua_resume( lua_State* L, lua_State* from, int nargs ) {
    int status;
    unsigned short oldnny = L->nny;  /* save "number of non-yieldable" calls */
    lua_lock( L );

    if ( L->status == LUA_OK ) { /* may be starting a coroutine */
        if ( L->ci != &L->base_ci ) { /* not in base level? */
            return resume_error( L, "cannot resume non-suspended coroutine", nargs );
        }
    }
    else if ( L->status != LUA_YIELD ) {
        return resume_error( L, "cannot resume dead coroutine", nargs );
    }

    L->nCcalls = ( from ) ? from->nCcalls + 1 : 1;

    if ( L->nCcalls >= LUAI_MAXCCALLS ) {
        return resume_error( L, "C stack overflow", nargs );
    }

    luai_userstateresume( L, nargs );
    L->nny = 0;  /* allow yields */
    api_checknelems( L, ( L->status == LUA_OK ) ? nargs + 1 : nargs );
    status = luaD_rawrunprotected( L, resume, &nargs );

    if ( status == -1 ) { /* error calling 'lua_resume'? */
        status = LUA_ERRRUN;
    }
    else {  /* continue running after recoverable errors */
        while ( errorstatus( status ) && recover( L, status ) ) {
            /* unroll continuation */
            status = luaD_rawrunprotected( L, unroll, &status );
        }

        if ( errorstatus( status ) ) { /* unrecoverable error? */
            L->status = cast_byte( status ); /* mark thread as 'dead' */
            seterrorobj( L, status, L->top ); /* push error message */
            L->ci->top = L->top;
        }
        else {
            lua_assert( status == L->status );    /* normal end or yield */
        }
    }

    L->nny = oldnny;  /* restore 'nny' */
    L->nCcalls--;
    lua_assert( L->nCcalls == ( ( from ) ? from->nCcalls : 0 ) );
    lua_unlock( L );
    return status;
}


LUA_API int lua_isyieldable( lua_State* L ) {
    return ( L->nny == 0 );
}


LUA_API int lua_yieldk( lua_State* L, int nresults, lua_KContext ctx,
                        lua_KFunction k ) {
    CallInfo* ci = L->ci;
    luai_userstateyield( L, nresults );
    lua_lock( L );
    api_checknelems( L, nresults );

    if ( L->nny > 0 ) {
        if ( L != G( L )->mainthread ) {
            luaG_runerror( L, "attempt to yield across a C-call boundary" );
        }
        else {
            luaG_runerror( L, "attempt to yield from outside a coroutine" );
        }
    }

    L->status = LUA_YIELD;
    ci->extra = savestack( L, ci->func ); /* save current 'func' */

    if ( isLua( ci ) ) { /* inside a hook? */
        api_check( L, k == NULL, "hooks cannot continue after yielding" );
    }
    else {
        if ( ( ci->u.c.k = k ) != NULL ) { /* is there a continuation? */
            ci->u.c.ctx = ctx;    /* save context */
        }

        ci->func = L->top - nresults - 1;  /* protect stack below results */
        luaD_throw( L, LUA_YIELD );
    }

    lua_assert( ci->callstatus & CIST_HOOKED ); /* must be inside a hook */
    lua_unlock( L );
    return 0;  /* return to 'luaD_hook' */
}


int luaD_pcall( lua_State* L, Pfunc func, void* u,
                ptrdiff_t old_top, ptrdiff_t ef ) {
    int status;
    CallInfo* old_ci = L->ci;
    lu_byte old_allowhooks = L->allowhook;
    unsigned short old_nny = L->nny;
    ptrdiff_t old_errfunc = L->errfunc;
    L->errfunc = ef;
    status = luaD_rawrunprotected( L, func, u );

    if ( status != LUA_OK ) { /* an error occurred? */
        StkId oldtop = restorestack( L, old_top );
        luaF_close( L, oldtop ); /* close possible pending closures */
        seterrorobj( L, status, oldtop );
        L->ci = old_ci;
        L->allowhook = old_allowhooks;
        L->nny = old_nny;
        luaD_shrinkstack( L );
    }

    L->errfunc = old_errfunc;
    return status;
}



/*
** Execute a protected parser.
*/
struct SParser {  /* data to 'f_parser' */
    ZIO* z;
    Mbuffer buff;  /* dynamic structure used by the scanner */
    Dyndata dyd;  /* dynamic structures used by the parser */
    const char* mode;
    const char* name;
};


static void checkmode( lua_State* L, const char* mode, const char* x ) {
    if ( mode && strchr( mode, x[0] ) == NULL ) {
        luaO_pushfstring( L,
                          "attempt to load a %s chunk (mode is '%s')", x, mode );
        luaD_throw( L, LUA_ERRSYNTAX );
    }
}


static void f_parser( lua_State* L, void* ud ) {
    LClosure* cl;
    struct SParser* p = cast( struct SParser*, ud );
    int c = zgetc( p->z ); /* read first character */

    if ( c == LUA_SIGNATURE[0] ) {
        checkmode( L, p->mode, "binary" );
        cl = luaU_undump( L, p->z, p->name );
    }
    else {
        checkmode( L, p->mode, "text" );
        cl = luaY_parser( L, p->z, &p->buff, &p->dyd, p->name, c );
    }

    lua_assert( cl->nupvalues == cl->p->sizeupvalues );
    luaF_initupvals( L, cl );
}


int luaD_protectedparser( lua_State* L, ZIO* z, const char* name,
                          const char* mode ) {
    struct SParser p;
    int status;
    L->nny++;  /* cannot yield during parsing */
    p.z = z;
    p.name = name;
    p.mode = mode;
    p.dyd.actvar.arr = NULL;
    p.dyd.actvar.size = 0;
    p.dyd.gt.arr = NULL;
    p.dyd.gt.size = 0;
    p.dyd.label.arr = NULL;
    p.dyd.label.size = 0;
    luaZ_initbuffer( L, &p.buff );
    status = luaD_pcall( L, f_parser, &p, savestack( L, L->top ), L->errfunc );
    luaZ_freebuffer( L, &p.buff );
    luaM_freearray( L, p.dyd.actvar.arr, p.dyd.actvar.size );
    luaM_freearray( L, p.dyd.gt.arr, p.dyd.gt.size );
    luaM_freearray( L, p.dyd.label.arr, p.dyd.label.size );
    L->nny--;
    return status;
}


